add avg-bitrate script

avg-bitrate.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+
+set -e
+
+get_bitrate() {
+	bitrate=$(ffprobe -v error -select_streams v:0 -show_entries stream=bit_rate -of default=noprint_wrappers=1:nokey=1 "$1")
+	echo $((bitrate/1000))
+}
+
+[ -z "$1" ] && {
+	echo "usage: $0 FILENAME [FILENAME ...]"
+	echo "   or: $0 *.mp4"
+	exit 1
+}
+
+total=0
+count=0
+
+while [ $# -gt 0 ]; do
+	if [ -f "$1" ]; then
+		vb=$(get_bitrate "$1")
+		total=$((total+vb))
+		count=$((count+1))
+	else
+		>&2 echo "error: $1: no such file"
+		exit 1
+	fi
+	shift
+done
+
+avg=$((total/count))
+echo "$avg kbps"